docs: def _find_executables(name):
      """ Try to find an executable.
      """
      exe_name = name + '.exe' * sys.platform.startswith('win')
      env_path = os.environ.get(name.upper()+ '_PATH', '')
      
      possible_locations = []
      def add(*dirs):
          for d in dirs:
              if d and d not in possible_locations and os.path.isdir(d):
                  possible_locations.append(d)
      
      # Get list of possible locations
      add(env_path)
      try:
          add(os.path.dirname(os.path.abspath(__file__)))
      except NameError:  # __file__ may not exist
          pass
      add(os.path.dirname(sys.executable))
      add(os.path.expanduser('~'))
      
      # Platform specific possible locations
      if sys.platform.startswith('win'):
          add('c:\\program files', os.environ.get('PROGRAMFILES'),
              'c:\\program files (x86)', os.environ.get('PROGRAMFILES(x86)'))
      else:
          possible_locations.extend(['/usr/bin','/usr/local/bin','/opt/local/bin'])
      
      def do_check_version(exe):
          try:
              return subprocess.check_output([exe, '--version']).decode().strip()
          except Exception:
              # print('not a good exe', exe)
              return False
      
      # If env path is the exe itself ...
      if os.path.isfile(env_path):
          ver = do_check_version(env_path)
          if ver:
              return env_path, ver
      
      # First try to find obvious locations
      for d in possible_locations:
          for exe in [os.path.join(d, exe_name), os.path.join(d, name, exe_name)]:
              if os.path.isfile(exe):
                  ver = do_check_version(exe)
                  if ver:
                      return exe, ver
      
      # Maybe the exe is on the PATH
      ver = do_check_version(exe_name)
      if ver:
          return exe_name, ver
          
      # Try harder
      for d in possible_locations:
          for sub in reversed(sorted(os.listdir(d))):
              if sub.startswith(name):
                  exe = os.path.join(d, sub, exe_name)
                  if os.path.isfile(exe):
                      ver = do_check_version(exe)
                      if ver:
                          return exe, ver
      
      return None, None